Slow Viewport Rendering: Bad Settings or Underequipped CPU?
Cloth Simulation can be pretty heavy. The normal usage is to cache your cloth simulation first, then render using the cached data.



Once you have your cloth sim cached to disc, it doesn't take any extra time to render each frame. But caching/baking the simulation can still take a while so it's important to use settings that fit your system and needs.

All the rendering settings won't have any real impact on the time calculating the cloth simulation takes. That time it takes depends heavily on the mesh complexity and your cloth quality settings.

The first step you should take is to use as simple a mesh as possible. You can add an additional subdivision modifier AFTER your cloth simulation to make the mesh smoother, while not adding tons of extra detail to your simulation.

Start with a very simple mesh and low quality settings on the simulation. Try to make the result look better with modifiers applied after the simulation before you increase subdivisions or quality settings that are part of the simulation.